Objective　To provide anatomic evidence for treating fracture dislocation of iliosacral articulation through the anterior approach.　Methods　The study was performed in 20 adult antiseptic pelvic specimen（from 40 corpses）. The relationship of the internal iliac vessels and the lumbar vessels with acroiliac articulation were explored. The distances from the anterior branches of L4,5 spinal nerves to the lumbosacral trunk and sacroiliac joint were measured.　Results　The external diameters of the left and right internal iliac arteries were (5.92±0.7)mm and (5.38±0.7)mm respectively, at the crossing point of the artery with sacroiliac joint. The distances from the arterial origin to pelvic wall were (11.91±2.4)mm and (12.52±2.9)mm for left and right sides respectively. The external diameters of iliolumbal artery when it passed through sacroiliac articulation was about (2.54±0.39)mm, with the distance from the origin to pelvic wall of (2.50±0.41)mm. The distance from the different sacroiliac articulation planes extended posterosuperiorly to anteroinferiorly to anterior branches of L4,5 spinal nerves and the lumbosacral trunk decreased gradually, as well the distances from anterior branch of L4 nerve root to ala sacralis. L5 nerve root closed to ala sacralis during it's course after leaving corresponding intervertebral foramen.　Conclusions　Iatrogenic injury to vessels and nerves during anterior operation for treating fracture dislocation of iliosacral articulation should be avoided．For avoiding the damage of L5 nerve root, the middle and superior parts of ala sacri, which is far away from the border of ala sacri about 20mm, are safe position for steel plate fixation.